In the construction industry, it is commonly necessary to provide an article of manufacture which is to be partially embedded in a surface such as a floor, wall or roof, so that only one side of the article is subsequently accessible. When it is required to attach another item to such a partially embedded article, in a releasable manner, the exposed side of the article must be provided with accessible securing means, such as screw threaded apertures or the like. The provision of screw threaded apertures machined into the accessible surface of an article substantially increases its cost of manufacture. Whilst such an arrangement may be acceptable in relatively expensive articles made of strong materials such as metal, it is often impractical with articles made of synthetic plastics material, because screw threads machined into plastic articles are commonly not strong enough to permit rigid securing of other items to them.
A particular example of an article of manufacture to which the present invention relates is a floor drain, having a depending cylindrical body and an upper peripheral flange. Such fittings are normally installed by being embedded in concrete, which is poured up to the level of the flange, so that the top surface of the drain is substantially flush with the floor surface. Then, items such as drain covers, grilles or the like have to be releasably secured to the top surface of the drain. After pouring and hardening of the concrete, of course, there is no access to the bottom surface of the flange, to position securing means such as nuts below apertures provided therein. Recent advances in the construction and plumbing industries have made the use of synthetic thermoplastic materials such as ABS highly desirable for the manufacture of floor drain units. As noted above, however, the machining of screw threaded apertures from the top flange surface of a plastic floor drain unit, to permit releasable attachment of drain covers and the like thereto, should be avoided.